#include <stdio.h>

int cal_total_expense(double price, int num) {
    double total;
    if (num <= 100) 
        total = price*num;
    else {
        total = price*100 + price*(num-100)*3/4;
    }
    return total;
}

int main()
{
    double price;
    int num;
    scanf("%lf%d", &price, &num);
    printf("%d\n",cal_total_expense(price, num));
    return 0;
}